Currently, there are many types of outdoor lighting fixtures available for lighting large areas such as parking lots, football fields, baseball diamonds, soccer fields and other types of sporting fields. The most common lighting fixtures used in floodlighting and sports lighting applications typically utilize high-intensity arc lamps such as metal halide, high pressure sodium or mercury lamps. However, most of the prior lighting fixtures currently on the market suffer from one or more disadvantages.
One of the most common types of lighting fixtures available on the market for floodlighting or sports lighting applications is the type with a symmetrical bowl-shaped reflector and an axially mounted, single-ended lamp. One common problem with such lighting fixtures is the glare produced therefrom. In the context of sports lighting and other outdoor lighting, glare occurs in these applications due to the contrast of the brightness of the light from the lighting fixture high up in the sky against the darkness of the sky. The glare can be quite annoying and discomforting. Accordingly, in sports lighting, this glare can cause a significant loss in visual performance for the viewer or fan watching the sporting event. In the case of floodlights in parking lots and along roadways, this glare can distract and obstruct a drivers' vision to sometimes cause an accident. Moreover, the higher the intensity of the lamp, the greater the problem with glare.
In view of this glare problem, many different types of modifications to the basic lighting fixture have been proposed. Many of which work quite well in controlling glare. However, these solutions often create their own problems, and/or are often expensive or difficult to manufacture and install.
One solution to controlling glare is to use an external visor attachment, which is coupled to the exterior peripheral edge of the lighting fixture. The external visor extends outwardly from the peripheral edge of the reflector and serves to block light, whether direct or reflected from the lamp, from traveling upwardly and outwardly. While the external visor does in fact control some of the glare, it also creates its own problem. Specifically, such an external visor can increase the wind resistance of the lighting fixture. Thus, the visor can be torn off by the wind, or even worse, the entire lighting fixture can be damaged by the wind.
Another solution to controlling the glare problem is utilizing special bulbs which are either painted along their upper surface or has a special attachment thereto. However, these special bulbs and/or special attachments can be difficult to install in high locations and/or expensive to manufacture.
In addition to the glare problem, arc lamps used with these lighting fixtures suffer from a problem called "tilt factor". In particular, the arc tube of an arc lamp is generally aligned along the longitudinal axis of the lamp so that orientation of the arc tube depends upon the orientation of the lamp. Generally, the lamp and arc tube are installed along the central aiming axis of the reflector. In other words, the longitudinal axis of the arc tube is coaxial with the longitudinal axis of the arc lamp, which in turn is coaxial with the longitudinal axis of the lamp mounting socket and the reflector. Accordingly, when the lighting fixture is aimed downwardly towards the field, the lamp and arc tube are also tilted downwardly towards the field. This downward tilting of the lamp causes the heat generated by the arc tube to rise to the highest point in the lamp. In other words, the upper end of the lamp towards the socket will become hotter than the lowest point of the lamp, which is generally at the lower front end of the lamp. These temperature differences can cause precipitation of some of the loaded chemicals inside the arc tube to cause clouding and blockage of the light. This clouding and blockage of the light results in lower efficiency of the lamp. If a conventional arc lamp is tilted below horizontal position, the tilt factor can result in light output loss of up to 20% depending upon the tilt.
Some prior lighting fixtures have attempted to overcome this "tilt factor" by utilizing special lamps and/or mounting the lamp at an angle relative to the main or central aiming axis of the reflector. However, these types of lighting fixtures only maintain the arc tube in the horizontal position when the lighting fixture is tilted to a particular angle. In other words, if the lighting fixture is adjusted to any other angle, the arc tube will no longer remain horizontal.
Another problem with most lighting fixtures utilizing lamps with arc tubes is that the majority of the light emitted from the lamp towards the area to be illuminated is reflected light rather than direct light. Specifically, arc lamps emit light in such a manner that the majority of the light emitted therefrom radiates radially from its longitudinal axis. In other words, a relatively small amount of light is radiated directly from the ends of the arc tube. Accordingly, arc tubes which are mounted along the longitudinal axis or central aiming axis of the reflector typically has the end of the arc tube pointed at the area to be lighted. Thus, most of the light from these types of lighting fixtures is reflected light rather than direct light. To solve this problem, many special lamps have been developed having angled arc tubes. However, these special lamps are more expensive and must be installed properly to maximize their efficiency.
Examples of some prior lighting fixtures known in the art are disclosed in U.S. Pat. Nos.: 2,040,821 to Benjamin; 2,142,467 to Waterbury; 4,947,303 to Gordin; 4,725,934 to Gordin; 5,075,828 to Gordin; 5,161,883 to Gordin; 5,211,473 to Gordin; and 5,313,379 to Lemons.
In view of the above, it is apparent that there exists a need for a lighting fixture within a mounting arm which supports and maintains the lamp substantially perpendicular to the central aiming axis regardless of the tilt of the lighting fixture. This invention addresses these needs in the art, along with other needs which will become apparent to those skilled in the art once given this disclosure.